This application requests a renewal of the Hematopoiesis Training Grant, which was founded in 1999 to address the shortage in training opportunities for scientists and physician-scientists with career interests in hematopoiesis and hematopoietic stem cell biology; and to provide a core scientific leadership in this growing discipline for the next generation. The Hematopoiesis Program is a multi-disciplinary, cross-departmental training program that capitalizes on the extensive resources of the University of Pennsylvania School of Medicine (PSOM), The Children's Hospital of Pennsylvania (CHOP), and the Wistar Institute; selects appointees from pools of highly qualified trainees enrolled in their various pre- and post-doctoral programs; and encompasses faculty trainers with extensive funding, publication, and mentoring achievements. The Hematopoiesis Program has trained 17 post-doctoral and 5 pre-doctoral scientists with PhD, MD, or MD-PHD degrees, and currently accommodates an additional 3 post-doctoral and 3 pre-doctoral appointees. The Program draws pre-doctoral candidates from the large and highly regarded PhD and MD-PhD programs at the PSOM; and post-doctoral applicants from the competitive hematology fellowship programs at PSOM and CHOP, and from leading laboratories throughout the nation. Research mentorship is provided by 24 scientifically and experientially diverse trainers with research interests that encompass virtually all areas of hematopoiesis. The academic elements of the Program include an integrated curriculum of coursework, seminars, laboratory work, mentoring and career counseling, presentation, and manuscript and grant writing, which are effectively combined to train new investigators in the fundamentals of hematopoiesis science. Trainees are evaluated on the basis of written and oral presentations, Individualized Development Plans, and status conferences with the PI/PD and both research and Program mentors. The success of this instructional approach is indicated by the number of appointees who have progressed to leadership positions in academia and industry, have been successfully funded following Program graduation, and have made significant contributions to the biomedical literature. The Hematopoiesis Program underwent a change in leadership in 2011 following the death of its previous PI/PD, prompting a comprehensive review of programmatic goals and policy that have strengthened the training experience and are expected to impact future outcomes evaluation. The review also identified a large pool of highly qualified pre-doctoral MD-PhD students at Penn with career interests in hematopoiesis; consequently, this application requests two additional positions that are dedicated to these combined-degree students, to encourage and support their career progression in this area. In sum, the Hematopoiesis Program is carefully designed to train individuals in the fundamentals of hematopoiesis, with a goal of developing research leadership in this important and growing area of human biology.